TEPCO Admits ‘Reactor Rupture’: ‘There Must Be A Large Leak’ In Reactor No. 1 – Similar Ruptures In No. 2 And No. 3 Reactors Possible

Coolant is escaping through a newly discovered opening in the Fukushima Daiichi nuclear power plant’s No. 1 reactor pressure vessel, a development that could slow efforts to prevent potential further radiation releases from the Japanese facility, Reuters reported on Thursday (see GSN, May 11).

Plant operator Tokyo Electric Power learned the container held less water than previously believed following repairs to monitoring equipment this week; the tank’s fluid quantity was roughly 16 feet short of the depth required to fully submerge atomic fuel if the material had remained in its intended position. The six-reactor site was severely damaged in the March 11 earthquake and tsunami that left more than 20,000 people dead or missing in Japan.

“There must be a large leak,” Tokyo Electric Power official Junichi Matsumoto said to reporters on Thursday. “The fuel pellets likely melted and fell, and in the process may have damaged … the pressure vessel itself and created a hole,” he said.

Ongoing water transfers have successfully curbed the escaped fuel’s temperature, though, and workers would keep pumping fluid into the system, Matsumoto said. The container’s water quantity suggests the rupture is likely several centimeters across, indicating the fuel might have made contact with the air early in the crisis, he said. The vessel’s surface heat level has since been contained between 100 and 120 degrees Celsius, he noted.

The plant operator would explore the option of pumping fluid into the reactor at a faster rate in an attempt to more fully submerge nuclear material in the vessel, Matsumoto said.

The reactor has received just under 10,400 metric tons of water to date, and the destination of the escaping fluid was uncertain, he said, adding powerful radioactivity complicated a possible direct inspection of the area by plant personnel (Yuto Kubota, Reuters, May 12). Much of the fluid could have moved to the reactor’s outer containment vessel, Kyodo News reported (Kyodo News I/Mainichi Daily News, May 12).

Similar ruptures might have developed in the plant’s No. 2 and No. 3 reactors if their nuclear material had heated to the point of losing its structure, Reuters quoted Matsumoto as saying. The firm was planning similar cooling efforts for those systems.

Tokyo Electric Power is due to reassess next Tuesday its schedule for bringing conditions at the plant under control. The company might push back planned milestones in the time line, sources warned; the plan calls for a reduction in radioactive contaminant releases within three months and a cold shutdown of plant reactors in three to six months. In cold shutdown, nuclear fuel rods within reactors are submerged in water that is kept under 100 degrees Celsius.

“It is necessary to make a reassessment of the condition of the nuclear reactor,” Japanese Chief Cabinet Secretary Yukio Edano said (Kubota, Reuters).

A mechanism could still be established to move water within the No. 1 reactor’s inner pressure vessel and outer container, Kyodo quoted Japanese Nuclear and Industrial Safety Agency Deputy Director General Hidehiko Nishiyama as saying (Kyodo News I).

Meanwhile, an anticipated probe of factors behind the Fukushima disaster would require around a year to complete, Japanese officials said on Wednesday.

Prime Minister Naoto Kan would soon authorize the creation of an autonomous investigatory body comprised of around 10 individuals. The group would contain academics, law specialists and Fukushima prefecture residents, the sources said. Panel members would have no links to past Japanese atomic planning, and the group’s key findings would be publicly disclosed, Kan said on Tuesday.

The group would have the power to summon Japanese officials and plant operator managers, who would be expected to disclose all material of interest to the probe.

Separate portions of the body would address reasons that March 11 earthquake and tsunami harmed the plant, means of limiting affected areas and possible government policy reforms, according to the officials. The group would develop an initial assessment before the end of 2011 and a follow-up analysis around the middle of 2012, they said (Kyodo News II/Mainichi Daily News, May 12).

Radioactive material concentrations in nearly 500 square miles of land either meet or exceed the evacuation threshold for the 1986 Chernobyl disaster, according to measurements collected last month by the Japanese government and the U.S. Energy Department. The Japanese Nuclear Safety Commission intends to establishing radiation monitoring sites for use in determining when evacuees could go back to their residences (Asahi Shimbun II, April 12).

Japan indicated it would soon begin removing farm animals from the 12-mile exclusion surrounding the Fukushima facility, Agence France-Presse reported on Thursday. More than 10,000 cattle in the area were abandoned in the crisis and died of starvation, according to agriculturalists (Agence France-Presse/Sydney Morning Herald, May 12).